This invention relates generally to a electronic circuit which can be used on a single phase alternating current circuit to emulate a polyphase alternating current circuit. The purpose of the present invention is to provide a simple method of demonstrating or testing electricity meters of the type which are intended for use in metering polyphase alternating current supplies.
Electricity meters are used to measure electricity use and demand. Typically, such meters are sold to electric utilities who use them to record electricity consumption and demand for billing and other purposes.
Electricity is typically generated and distributed as a three phase alternating current. However, many users only receive single phase service. Consequently, the typical residential electricity meter is a single phase electromechanical meter, and standard electricity outlets in the United States supply single phase 60 Hz, 120 volt alternating current (VAC).
Many commercial and industrial users require three-phase service. Consequently, their electricity is metered using so-called "polyphase" meters, of the type supplied by Schlumberger Industries, Inc., Norcross, Ga., the assignee of the present invention. An electronic, polyphase meter which was recently introduced by Schlumberger Industries, Inc., called the VECTRON.TM. electronic polyphase meter includes a feature, called SITESCAN.TM. which was implemented in firmware within the VECTRON.TM. meter. The SITESCAN.TM. feature enables the VECTRON.TM. meter to effectively determine whether there has been a problem in the installation or wiring to the VECTRON.TM. meter. Such problems can easily result, because metering of polyphase circuits involves the vector relationships between the voltage and current on the three phases supplied to the customer. Thus, if there is any incorrect wiring to any of the current transformers or voltage transformers in any of the three phases supplied, the meter cannot properly do its job. The purpose of the SITESCAN.TM. feature is to identify such problems at the time the VECTRON.TM. meter is installed. Yet another purpose of the SITESCAN.TM. feature is to identify any tampering which may have taken place following the installation of a VECTRON.TM. meter.
The foregoing features of the VECTRON.TM. meter, and of the SITESCAN.TM. feature may be demonstrated to meter personnel learning to use the features of the VECTRON.TM. meter and others, including potential customers for the VECTRON.TM. meter only when the VECTRON.TM. meter is connected to a three phase system. As such connections are not typically readily available, and as single phase 120 VAC power can be found virtually any place, it would be desirable to have a polyphase emulator available which works off a single phase alternating current circuit. Such an emulator could be simply plugged into virtually any wall socket which provides 120 VAC, and then plugged into the VECTRON.TM. meter to demonstrate the operation of the VECTRON.TM. meter, including the SITESCAN.TM. feature. Naturally, with suitable modifications, an emulator of the type described could also be used to demonstrate the operation of polyphase meters, other than the VECTRON.TM. meter.